1. Field of the Invention
The invention relates to catalytically hydroprocessing hydrocarbonaceous feeds using two reaction stages and a stripping stage in a single reaction vessel. More particularly the invention relates to catalytically hydroprocessing a hydrocarbonaceous feed with once-through hydrogen in two, cocurrent catalytic reaction stages. The first reaction stage produces a partially hydroprocessed liquid effluent which is stripped in a stripping stage and then passed into the second reaction stage. The stripped liquid effluent reacts with fresh hydrogen in the second stage to produce a hydroprocessed liquid. The stripping stage and both reaction stages are in the same reaction vessel.
2. Background of the Invention
Hydroprocessing involves removing at least a portion of a feed""s heteroatom compounds, changing the molecular structure of the feed, and combinations thereof, by reacting the feed with hydrogen in the presence of a suitable hydroprocessing catalyst. Hydroprocessing includes processes such as hydrogenation, hydrocracking, hydrotreating, hydroisomerization and hydrodewaxing, and therefore plays an important role in upgrading petroleum streams to meet increasingly stringent quality specifications. For example, there is an increasing demand for improved heteroatom removal, particularly sulfur and nitrogen, improved aromatic compound saturation, and an overall boiling point reduction for some hydrocarbon fractions. Conventional hydroprocessing configurations have been developed which employ multiple vessels with both hydroprocessing and stripping stages. Some of the more recent configurations are disclosed, for example, in U.S. Pat. Nos. 5,705,052; 5,720,872; 5,968,346 and 5,985,135.
Environmental regulations have led to increasingly stringent hydrocarbon product specifications. Consequently, feeds and product streams require more upgrading in order to meet tighter specifications.
As the availability of lighter and cleaner feeds continues to decrease, hydroprocessing feeds may include more relatively high boiling feeds derived from such materials as coal, tar sands, shale oil, and heavy crudes, all of which typically contain significantly more undesirable components, such as halides, metals, unsaturates, and heteroatoms such as sulfur, nitrogen, and oxygen. There is therefore a need to further reduce the levels of undesirable components in hydroprocessing products, while employing feeds that increasingly contain significant amounts of undesirable species. It is not always possible or economically viable to construct a new, grass roots hydroprocessing facility within an existing refinery and, furthermore, most existing facilities have space constraints which limit or prevent adding additional reaction vessels, strippers, and associated utilities, to increase the extent of product hydroprocessing, hydroprocessing capacity, or both. There is therefore a need for cost-effective methods for increasing the hydroprocessing capacity of an existing hydroprocessing facility, increasing the purity of the hydroprocessed product, or both, without having to add multiple hydroprocessing reaction vessels and strippers.
In one embodiment, the invention is a hydroprocessing process comprising:
(a) reacting a hydrocarbonaceous feed with hydrogen in a first hydroprocessing reaction stage, in the presence of a first catalytically effective amount of a hydroprocessing catalyst, under first catalytic conversion conditions, to form a first stage effluent comprising a hydroprocessed hydrocarbonaceous liquid and a vapor;
(b) separating said first stage liquid and vapor effluents;
(c) stripping said first stage liquid effluent with a stripping gas in a stripping stage to produce at least a stripped liquid and a stripping vapor;
(d) combining said first stage vapor effluent and said stripping vapor and removing them from said vessel;
(e) passing said stripped liquid and fresh hydrogen or a fresh hydrogen treat gas into said second liquid stage in which they react in the presence of a second catalytically effective amount of a second hydroprocessing catalyst under second catalytic conversion conditions, to produce a second stage effluent comprising a hydroprocessed liquid product and a vapor which contains unreacted hydrogen, the first hydroprocessing stage, second hydroprocessing stage, and stripping stage being in a common vessel;
(f) passing said second stage vapor effluent into said first stage; and
(g) removing said hydroprocessed liquid product from said vessel.
In another embodiment, the invention is a method for upgrading an existing hydroprocessing facility for hydroprocessing a hydrocarbonaceous feed, this hydroprocessing facility comprising one or more reaction vessels, strippers and associated equipment, to produce a hydroprocessed hydrocarbonaceous liquid, comprising the steps of:
(a) passing hydrogen and a hydrocarbonaceous feed which has been at least partially hydroprocessed by said existing facility into a first reaction stage in which they react in the presence of a catalytically effective amount of a first hydroprocessing catalyst under first catalytic conversion conditions, to produce a first stage effluent comprising (i) a further hydroprocessed liquid, and (ii) a vapor;
(b) separating said first stage liquid and vapor effluents;
(c) stripping said first stage liquid effluent in a stripping stage to remove strippable dissolved compounds produced by said first stage reaction to produce at least a stripped liquid and a stripping vapor;
(d) combining said first stage vapor effluent and said stripping vapor;
(e) passing said stripped liquid and fresh hydrogen or a fresh hydrogen treat gas into a second reaction stage, in which they react in the presence of a catalytically effective amount of a second hydroprocessing catalyst under second catalytic conversion conditions to produce a second stage effluent comprising a hydroprocessed hydrocarbonaceous liquid product and a vapor which contains unreacted hydrogen, the first reaction stage, second reaction stage, and stripping stage being in a common upgrading vessel;
(f) separating said second stage liquid and vapor effluents and recovering said liquid as hydroprocessed hydrocarbonaceous liquid product and passing said second stage vapor effluent into said first stage;
(g) recovering said hydroprocessed liquid product and wherein said upgrading vessel has been added to, or has replaced a vessel in, said existing hydroprocessing facility; and
(h) conducting said combined first stage vapor effluent and said stripping vapor away from said upgrading vessel.